The Research On Microstructure And Performance Of Ni-Cu-W Coating Prepared By High Throughput

In order to achieve the goal of halving the research and development time and cost of advanced materials,it is urgent to develop high-throughput preparation technology for the preparation and screening of new materials.Exploring and developing a combination material chip,which is suitable for rapid,efficient and preparation of multiple composition gradients,has become a definitely groping way in the current research and development process of advanced materials.For the preparation and development of advanced alloy structural materials,there are three factors must be considered:(1)The high melting point of the elemental element and the melting points of different elements before alloying;(2)The uniformity of alloy melting in a short time;(3)The different scale structures of the same composition alloys.In addition,the standardization of raw materials,for the high-throughput preparation of alloy materials,must also be taken into consideration.In terms of the above four factors,we choose plasma spraying technology is regarded as the method of high-throughput preparation of alloy materials.In this paper,with the Ni-Cu-W alloy being taken as an example,a one-dimensional gradient coating is prepared by plasma spraying,and which is remelted by a laser post-treatment process to further improve the structure and performance of the coating.The gradient changing analyzed by scanning electron microscope,EDS and other test methods,combines the corrosion performance and friction and wear properties of different coatings to construct the combination relationship of composition-structure-performance,quickly screening out the optimal composition range.The composition of Ni-Cu-W coating prepared by plasma spraying technology shows a gradient distribution along the moving direction of the spraying torch,with the coating presenting different microstructure morphologies along the gradient direction.As the spraying current increases,the higher the flame temperature is,the more particles on the coating surface are fully melt,and the flatness of the coating surface is better.When the arc current is 450 A,there are no unmelted particles on the surface and the roughness is the lowest.At the same time,the moving speed of the spraying gun is too slow or too fast will affect the quality of the coating.The moving speed is too slow,resulting in cracking due to thermal stress.The coating is too thin because the moving speed is too fast.The coating and the substrate are combined closely when the moving speed is 10 mm/s.As the laser power increases,the elements are more fully mixed in the molten pool,with the matrix elements diffusing due to high temperature.When the laser power is 450 W,the coating surface has fewer pores,the best flatness,arc-shaped ripples,and fewer micro-cracks.The laser scanning speed also has a significant influence on the surface of the coating.If the scanning speed is too slow,it will lead to overburning.If too fast,the elements in the coating cannot be fully miscible.When the scanning speed is 4 mm/s,the large crack defect disappears and the complete solid solution is formed.The study of the microhardness after laser remelting in this paper found that the hardness value peak appears in the sample 3#(Ni: 55 wt.%-65 wt.%,Cu: 34 wt.%-44 wt.%,W: 0.1 wt.%-1 wt.%),and the element composition corresponding to the hardness value peak is Ni: 62.71±2.21 wt.%,Cu: 36.63±2.43 wt.%,W:0.66±0.21 wt.%.The corrosion and wear research of the coating before and after laser remelting found that the corrosion potential of sample 3# is the most positive,the corrosion current density the smallest,the impedance the largest,and the corrosion rate is the smallest.Compared with plasma sprayed samples,the samples after laser remelting have weaker corrosion tendency,lower corrosion density,wider passivation interval,and superior corrosion resistance.The friction coefficients of the three samples are 1.67±0.03 at the initial,1.58±0.03 at the middle,1.4±0.02 at the terminative,respectively.and the terminative(Ni: 60 wt.%-69 wt.%,Cu: 29 wt.%-40 wt.%,W: 0.1 wt.%-1 wt.%)has the smallest friction coefficient and the best wear performance.At the same time,the surface morphology of the gradient coating after abrasion shows different morphologies,mainly in the form of plough marks,cracks and debris.The wear mechanisms are mainly abrasive wear,delamination wear and oxidative wear.Combined with the analysis of the hardness value,the optimal composition range is: Ni: 62.71±2.21 wt.%,Cu: 36.63±2.43 wt.%,W:0.66±0.21 wt.%.